Date of Award


Degree Type


Degree Name

Doctor of Philosophy (PhD)


Horticulture and Landscape Architecture

First Advisor

Michael V. Mickelbart

Committee Chair

Michael V. Mickelbart

Committee Member 1

Clint Chapple

Committee Member 2

Brian P. Dilkes

Committee Member 3

David Rhodes


Water-use efficiency (WUE), the ratio of biomass to water loss, is a heritable but complex trait, the genetic basis of which is largely unknown. We utilized diverse accessions of the halophyte Eutrema salsugineum to ultimately identify a novel genetic determinant of WUE. E. salsugineum accessions from locations with low water availability, temperature, and radiation have lower transpirational water loss and greater biomass, resulting in higher WUE. High-WUE accessions also have lower stomatal density and index and larger thinner leaves than low-WUE accessions. We identified 14,808 single nucleotide polymorphisms (SNPs) between two accessions of E. salsugineum,Shandong (SH) and Yukon (YK), with low and high WUE, respectively. YK accumulates as much as 2-times biomass while losing only 1.5-times water as SH, resulting in greater WUE. The higher WUE in YK is partially attributable to more efficient carbon assimilation into biomass, and reduced carbon anabolism. YK accumulates higher concentrations of free fatty acids and long-chain fatty acid derivatives than SH; whereas starch and sugars are more abundant in SH. The new and previously published SNPs were used to identify quantitative trait loci (QTL) correlated with WUE and/or biomass using a YK x SH F2 bulked segregant analysis. Candidate genes were screened in A. thaliana mutants. TAF10 encodes one of the thirteen TATA-box binding protein associated factor (TAF) constituents of the TFIID complex and a loss-of-function mutant (taf10) has a 16% increase in WUE without a decrease in biomass production, relative to wild type (WT) plants. The improved WUE is due to a decrease in transpirational water loss that is correlated with smaller stomata. Transcriptome profiling between taf10 and WT plants suggests that mis-regulated auxin-responsive genes in taf10 may be correlated with small epidermal cell size phenotype. In this set of experiments, we used natural genetic variation of a complex trait to identify a general transcription factor that may play a role in plant adaptation to low-water-availability environments via modulation of WUE.